The present invention relates to irrigation systems and, in particular, it concerns an irrigation system and method which achieve a conical flow path.
In the field of drip irrigation, there is a natural tendency towards non-uniform release of water along the length of an irrigation tube due to variations in supply pressure and pressure loss due to energy losses and accumulated release of water along the length of the tube. The common approach to ensuring a roughly uniform distribution of water along the length of the tube is to provide irrigation tubes with pressure-regulating drip emitters installed along the tube. The pressure-regulating drip emitters are themselves a significant component of the cost of such products, and the manufacturing process is greatly complicated by the need to deploy the emitters correctly within the tube and ensure that perforation of the tube wall is spatially coordinated with the emitter positions.
Various attempts have been made to achieve regulation of water release from drip apertures without requiring insertion of distinct drip emitters within the tube. Examples of such attempts may be found in U.S. Pat. Nos. 4,473,191 to Chapin and 5,620,143 to Delmer et al. In these devices, attempts are made to produce structures similar to the aforementioned drip emitters by embossing structures into a region of a flat extruded strip which is then sealed to itself with overlap to form a tube. In these cases too, the production techniques are complex.
An alternative approach to controlled irrigation is the use of porous-wall irrigation tubes. These tubes are particularly suited to subterranean use since their porous properties are not compromised by the presence of mud and dirt, and therefore offer advantages of reduced evaporation losses, reduced maintenance problems and high proximity to the roots of the plants. However, such porous irrigation tubes also suffer from a pronounced problem of non-uniform flow rates, with greater amounts of water being released at the higher pressure supply end of the line than at the opposite end.
There is therefore a need for an irrigation system which would employ an easily produced tube structure which provides relatively uniform release of water drops along its length.